全文获取类型
收费全文 | 4147篇 |
免费 | 375篇 |
国内免费 | 181篇 |
专业分类
电工技术 | 255篇 |
综合类 | 490篇 |
化学工业 | 318篇 |
金属工艺 | 91篇 |
机械仪表 | 157篇 |
建筑科学 | 1027篇 |
矿业工程 | 197篇 |
能源动力 | 160篇 |
轻工业 | 247篇 |
水利工程 | 211篇 |
石油天然气 | 315篇 |
武器工业 | 21篇 |
无线电 | 221篇 |
一般工业技术 | 295篇 |
冶金工业 | 276篇 |
原子能技术 | 34篇 |
自动化技术 | 388篇 |
出版年
2024年 | 10篇 |
2023年 | 47篇 |
2022年 | 87篇 |
2021年 | 130篇 |
2020年 | 125篇 |
2019年 | 98篇 |
2018年 | 105篇 |
2017年 | 118篇 |
2016年 | 136篇 |
2015年 | 130篇 |
2014年 | 311篇 |
2013年 | 257篇 |
2012年 | 340篇 |
2011年 | 367篇 |
2010年 | 266篇 |
2009年 | 233篇 |
2008年 | 225篇 |
2007年 | 286篇 |
2006年 | 267篇 |
2005年 | 230篇 |
2004年 | 180篇 |
2003年 | 169篇 |
2002年 | 141篇 |
2001年 | 97篇 |
2000年 | 72篇 |
1999年 | 46篇 |
1998年 | 37篇 |
1997年 | 24篇 |
1996年 | 29篇 |
1995年 | 30篇 |
1994年 | 17篇 |
1993年 | 17篇 |
1992年 | 11篇 |
1991年 | 13篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1965年 | 2篇 |
1962年 | 1篇 |
1961年 | 1篇 |
1960年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1956年 | 2篇 |
排序方式: 共有4703条查询结果,搜索用时 15 毫秒
1.
Jarosaw Widelski Simon Vlad Luca Adrianna Skiba Monika Macig Barbara Budzyska Laurence Marcourt Jean-Luc Wolfender Krystyna Skalicka-Wo
niak 《International journal of molecular sciences》2021,22(4)
Different types of anxiety disorders have become the number one mental health issue in developed countries. The search for new, safer and effective drug-like molecules among naturally derived substances faces two difficulties: an efficient method of isolation compounds with a high-purity and high-throughput animal model for activity assay. Thus, the aim of the present study was to isolate by liquid–liquid chromatography high-purity rare coumarins from the fruits of Seseli devenyense Simonk. and evaluate their anxiolytic effect (defined as reversed thimotaxis) using a 5-days post-fertilization (dpf) Danio rerio larvae model. Liquid–liquid chromatography enabled the isolation of one simple hydroxycoumarin (devenyol) and four pyranocoumarins (cis-khellactone, d-laserpitin, isolaserpitin and octanoyllomatin). The anxiolytic effect was defined as a decrease in the time spent in the boundaries of the living space (also described as reversed thigmotaxis). Our results show that all isolated courmarins exerted a significant influence on the anxiety behavior (anxiolytic activity) in the zebrafish larvae model. According to our knowledge, this is the first report of anxiolytic activity of pyranocoumarins and devenyol. 相似文献
2.
For industrial chemical process, preliminary-summation-based principal component analysis (PS-PCA), an amended PCA method was recently provided for coping with both Gaussian and non-Gaussian characteristics. By summing the training and monitoring data respectively, PS-PCA is capable of resolving the issue of non-Gaussian processes and achieves higher fault detection rate than the traditional PCA. However, in the PS-PCA summation operation, all data samples are regarded as the same weight, which results in the fault information of newly-samples may be diluted, leading to significant detection delays. To address this challenge, in this paper, we propose a novel weighted PS-PCA (WPS-PCA) method that employs an exponential weighting scheme to put more emphasis on recent information. Subsequently, a mathematical argument demonstrates that when the number of variables is enough plentiful, the obtained summation combined with the generalized central limit theorem conforms to approximately a Gaussian distribution. The kurtosis relationships indicate this conversion will bring out well-pleasing feasibility for conventional PCA. Ultimately, the proposed technique verifies detection performance using the Tennessee Eastman process, which is compared with the existing PCA and PS-PCA schemes, in terms of the fault detection time and fault detection rate. The simulation studies reveal that the proposed method is efficient and superior. 相似文献
3.
Friederike Freiin von Hvel Ekaterini Kefalakes Claudia Grothe 《International journal of molecular sciences》2021,22(1)
Fibroblast growth factor 2 (FGF-2), ubiquitously expressed in humans and mice, is functionally involved in cell growth, migration and maturation in vitro and in vivo. Based on the same mRNA, an 18-kilo Dalton (kDa) FGF-2 isoform named FGF-2 low molecular weight (FGF-2LMW) isoform is translated in humans and rodents. Additionally, two larger isoforms weighing 21 and 22 kDa also exist, summarized as the FGF-2 high molecular weight (FGF-2HMW) isoform. Meanwhile, the human FGF-2HMW comprises a 22, 23, 24 and 34 kDa protein. Independent studies verified a specific intracellular localization, mode of action and tissue-specific spatiotemporal expression of the FGF-2 isoforms, increasing the complexity of their physiological and pathophysiological roles. In order to analyze their spectrum of effects, FGF-2LMW knock out (ko) and FGF-2HMWko mice have been generated, as well as mice specifically overexpressing either FGF-2LMW or FGF-2HMW. So far, the development and functionality of the cardiovascular system, bone formation and regeneration as well as their impact on the central nervous system including disease models of neurodegeneration, have been examined. This review provides a summary of the studies characterizing the in vivo effects modulated by the FGF-2 isoforms and, thus, offers a comprehensive overview of its actions in the aforementioned organ systems. 相似文献
4.
5.
Benedetta Russo Marika Menduni Patrizia Borboni Fabiana Picconi Simona Frontoni 《International journal of molecular sciences》2021,22(10)
The role of the autonomic nervous system in obesity and insulin-resistant conditions has been largely explored. However, the exact mechanisms involved in this relation have not been completely elucidated yet, since most of these mechanisms display a bi-directional effect. Insulin-resistance, for instance, can be caused by sympathetic activation, but, in turn, the associated hyperinsulinemia can activate the sympathetic branch of the autonomic nervous system. The picture is made even more complex by the implicated neural, hormonal and nutritional mechanisms. Among them, leptin plays a pivotal role, being involved not only in appetite regulation and glucose homeostasis but also in energy expenditure. The purpose of this review is to offer a comprehensive view of the complex interplay between leptin and the central nervous system, providing further insights on the impact of autonomic nervous system balance on adipose tissue and insulin-resistance. Furthermore, the link between the circadian clock and leptin and its effect on metabolism and energy balance will be evaluated. 相似文献
6.
采用中心复合设计的响应曲面法预测电催化降解染料废水的最优条件。具体以Ti/SnO2-Sb 电极作为阳极,应用响应曲面法研究了pH、施加电压值、电极间距对亚甲基蓝溶液脱色效率的影响。研究结果表明模型拟合精度R2=0.9942,初始pH、施加电压值、电极间距及交互作用对脱色率响应值影响大。模型预测最佳反应条件pH为 6.98,施加电压6.0 V,电极间距为1.01 cm时,脱色效率预测值达到98.68%。采用实验进一步验证该模型,预测最佳条件下三次实验脱色率平均值98.47%。该方法可用于优化电催化降解染料废水的工艺参数,为实际废水处理提供优化方案。 相似文献
7.
Immobilized lipase catalyzed synthesis of n‐amyl acetate: parameter optimization,heterogeneous kinetics,continuous flow operation and reactor modeling 下载免费PDF全文
8.
9.
加强土地市场监管 ,必须着重从体制、机制和法治上解决问题。一要完善法规体系 ,真正做到有法可依。二要健全执法体系 ,真正做到有法必依。三要扩大执法成果的应用 ,建立快速执法机制。四要建立巡查责任制 ,及时制止违法行为发生。 相似文献
10.
本文介绍江西省10座矿业城市基本情况并进行了初步分析。这些城市全都属于有依托型矿城,大多数资源保证程度较好,但采矿活动引起的环境问题很严重。有些矿城有望建成区域性中心城市。 相似文献